I am listening to on of the celebrity using Twitter4j Api which uses twitter streaming Api.
As soon as he tweet I get the Id or idstr and reply to him by mentioning his name.
Earlier my reply would be first of all the tweet now from 1-2 month it is not showing as reply or sometime it shows above his tweet look like a bug.
Let me know if it is expected

There’s no API that guarantees that replies will cause a user to be notified or a conversation to be threaded.

If your posts or your app are deemed to be of low quality, are reported as spammy, or otherwise are affected by our antispam and safety tools, then the Tweets may not appear in the user interface or notifications.

Spamming: You may not send automated Tweets or Direct Messages that are spam, or otherwise engage in spamming activity. Some examples of spammy behavior to avoid with automation include:

Trending topics: You may not automatically post about trending topics on Twitter, or use automation to attempt to influence or manipulate trending topics.
Multiple posts/accounts: You may not post duplicative or substantially similar Tweets on one account or over multiple accounts you operate.